Erratum to: "Anxiety and neurometabolite levels in the hippocampus and amygdala after prolonged exposure to predator-scent stress".

Vavilovskii Zhurnal Genetiki i Selektsii = Vavilov Journal of Genetics and Breeding. 2019;23(5):582-587 (in Russian) Page 587, in Acknowledgements instead of The animals and behavioral testing are supported by the budget project (No. 0324-2019-0041). The MRI study is supported by the budget project (No. 0259-2019-0004). All studies are implemented using the equipment of Center for Genetic Resources of Laboratory Animals at ICG SB RAS, supported by the Ministry of Education and Science of Russia (Unique ID# of the project: RFMEFI62117X0015). should read The animals and behavioral testing are supported by the budget project (No. 0324-2019-0041). The MRI study is supported by the budget project (No. 0259-2019-0004). All studies are implemented using the equipment of Center for Genetic Resources of Laboratory Animals at ICG SB RAS, supported by the Ministry of Education and Science of Russia (Unique ID# of the project: RFMEFI62117X0015). The study was conducted within the basic part of the state task of the Ministry of Science and Higher Education of the Russian Federation (No. 17.7255.2017/8.9). The original article can be found under DOI 10.18699/VJ19.528.

Physical Fatigue and Morphofunctional State of the Myocardium in Experimental Chronic Stress.

The relationship between the development of skeletal muscle fatigue of a specific type in male Wistar rats and morphofunctional alterations in the myocardium in the posttraumatic stress disorder (PTSD) model has been investigated for the first time. The aggravation of oxidative stress in the cardiomyocytes and the related transformation of the cell structural components and the depletion of energy reserves in PTSD has been identified as one of the main factors that accelerate the onset of musculoskeletal fatigue.

[Effect of adaptation to hypoxia on expression of NO synthase isoforms in rat myocardium].

Previously we have shown that adaptation to hypoxia (AH) is cardio- and vasoprotective in myocardial ischemic and reperfusion injury and this protection is associated with restriction of nitrosative stress. The present study was focused on further elucidation of NO-dependent mechanisms of AH by identifying specific NO synthases (NOS) that could play the major role in AH protection. AH was performed in a normobaric hypoxic chamber by breathing hypoxic gas mixture (9.5-10% O2) for 5-10 min with intervening 4 min normoxia (5-8 cycles daily for 21 days). Expression of neuronal (nNOS), inducible (iNOS), and endothelial (eNOS) protein was measured in the left ventricular myocardium using Western blot analysis with respective antibodies. AH educed iNOS protein expression by 71% (p < 0.05) whereas eNOS protein expression tended to be reduced by 41% compared to control (p < 0.05). nNOS protein expression remained unchanged after AH. Selective iNOS inhibition can mimic the AH-induced protection. Therefore protective effects of AH could be at least partially due to restriction of iNOS and, probably, eNOS expression.

[Vasoprotective effect of adaptation to hypoxia in myocardial ischemia and reperfusion injury].

Adaptation to hypoxia is known to be cardioprotective in ischemic and reperfusion (IR) injury of the myocardium. This study was focused on investigating a possibility for prevention of endothelial dysfunction in IR injury of the rat heart using adaptation to intermittent hypoxia, which was performed in a cyclic mode (5-10 min of hypoxia interspersed with 4 min of normoxia, 5-8 cycles daily) for 21 days. Endothelial function of coronary blood vessels was evaluated after the in vitro IR of isolated heart (15 min of ischemia and 10 min of reperfusion) by the increment of coronary flow rate in response to acetylcholine. Endothelium-dependent relaxation of isolated rat aorta was evaluated after the IR myocardial injury in situ (30 min of ischemia and 60 min of reperfusion) by a relaxation response of noradrenaline-precontracted vessel rings to acetylcholine. The following major results were obtained in this study: 1) IR myocardial injury induced endothelial dysfunction of coronary blood vessels and the aorta, a non-coronary blood vessel, remote from the IR injury area; and 2) adaptation to hypoxia prevented the endothelial dysfunction of both coronary and non-coronary blood vessels associated with the IR injury. Therefore, adaptation to hypoxia is not only cardioprotective but also vasoprotective in myocardial IR injury.

[Resistance to acute hypoxia and changes in the phenotype and phenotypic plasticity of macrophages in mice of different genetic strains].

The aim of study was to investigate the effect of hypoxia on the macrophage phenotype and phenotypic plasticity and to determine the resistance to acute hypoxia in C57/BL mice, which have the pro-inflammatory M1 macrophage phenotype, and in BALB/c mice, which have the anti-inflammatory M2 macrophage phenotype. The following results were obtained. 1) The response of macrophages to acute hypoxia has two successive phases, the immediate, anti-inflammatory phase, and the delayed, pro-inflammatory phase. This response was more distinctly inverted in C57/BL6 M1 macrophages than in BALB/c M2 macrophages; 2) the effect of acute hypoxia on macrophage phenotypic plasticity depends on the genetically predetermined, original macrophage phenotype. In this process, a clear regularity was observed: hypoxia increased the capability of macrophages for changing into the pro-inflammatory M1 phenotype, while their capability for changing into the anti-inflammatory M2 phenotype remained virtually unaffected. 3) BALB/c mice were more resistant to acute hypoxia than C57/BL6 mice. Taken together, these data expand our understanding of mechanisms for pathogenetic effects of hypoxia.

[Role of restricted nitric oxide overproduction in the cardioprotective effect of adaptation to intermittent hypoxia].

Adaptation to intermittent normobaric hypoxia is cardioprotective and can stimulate nitric oxide (NO) synthesis. However the role of nitric oxide (NO) in prevention of ischemia-reperfusion (IR) injury of myocardium is controversial. This study was focused on evaluating the effect of adaptation to hypoxia and IR on NO production and development of nitrative stress in the myocardium. Adaptation to hypoxia tended to increase NO production, which was determined by the total level of plasma nitrite and nitrate, and prevented IR-induced NO overproduction. The IR-induced NO overproduction was associated with significant 3-nitrotyrosine (3-NT) accumulation in the left ventricle but not in septum or aorta. In hypoxia-adapted rats, 3-NT after IR was similar to that of control rats without IR. IHC induced marked accumulation of HIF-1alpha in the left ventricle. We suggest that HIF-1alpha contributes to NO-synthase expression during adaptation to hypoxia and thereby facilitates the increase in NO production. NO, in turn, may subsequently prevent NO overproduction during IR by a negative feedback mechanism.

Prevention of neurodegenerative damage to the brain in rats in experimental Alzheimer's disease by adaptation to hypoxia.

We report here studies addressing the possibility of preventing neurodegenerative changes in the brain using adaptation to periodic hypoxia in rats with experimental Alzheimer's disease induced by administration of the neurotoxic peptide fragment of beta-amyloid (Ab) into the basal magnocellular nucleus. Adaptation to periodic hypoxia was performed in a barochamber (4000 m, 4 h per day, 14 days). The following results were obtained 15 days after administration of Ab. 1. Adaptation to periodic hypoxia significantly blocked Ab-induced memory degradation in rats, as assessed by testing a conditioned passive avoidance reflex. 2. Adaptation to periodic hypoxia significantly restricted increases in oxidative stress, measured spectrophotometrically in the hippocampus in terms of the content of thiobarbituric acid-reactive secondary lipid peroxidation products. 3. Adaptation to periodic hypoxia completely prevented the overproduction of NO in the brains of rats with experimental Alzheimer's disease, as measured in terms of increases in tissue levels of stable NO metabolites, i.e., nitrites and nitrates. 4. The cerebral cortex of rats given Ab injections after adaptation to periodic hypoxia did not contain neurons with pathomorphological changes or dead neurons (Nissl staining), which were typical in animals with experimental Alzheimer's disease. Thus, adaptation to periodic hypoxia effectively prevented oxidative and nitrosative stress, protecting against neurodegenerative changes and protecting cognitive functions in experimental Alzheimer's disease.

[Prevention of the brain neurodegeneration in rats with experimental Alzheimer's disease by adaptation to hypoxia].

The study focused on a possibility of preventing brain neurodegeneration by adaptation to intermittent hypoxia (AH) in rats with experimental Alzheimer's disease (AD) modeled by injection of a neurotoxic bert-amyloid peptide fragment (Ab) into n. basalis magnocellularis. AH was produ- ced in an altitude chamber (4.000 m; 4 hours daily; 14 days). The following results were obtained after fifteen days of the Ab injection: (1) AH substantially prevented the memory impairment induced by Ab, which was determined using the conditioned avoidance reflex test; (2) the AH significantly restricted the enhanced oxidative stress, which was determined spectrophotometrically by thiobarbituric acid-reactive substance level in the hippocampus; (3) the AH completely prevented Ab-induced nitric oxide (NO) overproduction in brain, which was measured by tissue level of nitrite and nitrate; (4) pathologically changed and dead neurons (Niessle staining) were absent in the brain cortex of rats exposed to AH before the Ab injection. Therefore AH seems to effectively prevent oxidative and nitrosative stress thereby providing protection of brain against neurodegeneration and preservation of cognitive function in experimental AD.

[Organ specificity in nitric oxide storage in the blood vessel walls during adaptation to hypoxia].

Addition of N-acetylcysteine induced relaxation of the coronary and basilar arteries thus indicating some basilar NO-stores in these vessels. The maximum capacity of the NO-stores was similar in the coronary and the basilar arteries. Following adaptation to hypoxia, however, the depot was much greater in the coronary artery wall. This seems to be connected with different degree of participation of the NO-dependent vasodiatation in implementation of the adaptive response to hypoxia in coronary and cerebral vascular systems.

Role of nitric oxide in prevention of cognitive disorders in neurodegenerative brain injuries in rats.

NO synthesis disturbances play an important role in the development of neurodegenerative damage in Alzheimer disease. We previously showed that adaptation to intermittent hypobaric hypoxia prevents cognitive disturbances in rats with experimental Alzheimer disease. Here we evaluated the role of NO in cognitive disorders and development of adaptive protection during experimental Alzheimer disease. Adaptation to hypoxia in rats was performed in a hypobaric pressure chamber at a simulated altitude of 4000 m (4 h per day for 14 days). Alzheimer disease was simulated by bilateral injections of a toxic fragment of beta-amyloid (25-35) into n. basalis magnocellularis. For evaluation of the role of NO in the development and prevention of memory disorders, the rats received intraperitoneally either NO-synthase inhibitor N omega-nitro-L-arginin (L-NNA, 20 mg/kg, every other day for 14 days) or NO-donor dinitrosyl iron complex (200 microg/kg daily for 14 days). NO-synthase inhibitor potentiated the damaging effect of beta-amyloid, abolished the protective effect of adaptation to hypoxia, and produced memory disorders in rats similar to those observed during experimental Alzheimer disease. In contrast, the increase in NO level in the body provided by injections of the NO-donor produced a protective effect against memory disorders caused by beta-amyloid similar to that induced by adaptation to hypoxia. We concluded that reduced NO production in the organism plays an important role in the development of cognitive disorders produced by injections of beta-amyloid, while prevention of NO deficit by administration of NO-donors or non-pharmacological stimulation of NO synthesis can provide a protective effect in experimental Alzheimer disease.

Antiarrhythmic effect of heat adaptation in ischemic and reperfusion injury to the heart.

Study on a model of 6-day dosed adaptation to heat in rats showed that this adaptation decreased the severity of cardiac arrhythmias during ischemic and reperfusion injury. The duration of arrhythmias decreased not only in the ischemic period, but also under conditions of reperfusion. Adaptation delayed the development of arrhythmias during ischemia, decreased the number of animals with late reperfusion arrhythmias, and improved recovery of the heart after ischemia and reperfusion.

[Clinical significance of nitric oxide levels in patients with chronic glomerulonephritis].

Nitric oxide (NO) takes an active part in the regulation of the main renal functions, water-salt metabolism, and system arterial pressure. Under pathological conditions, NO plays the leading role in the development and progression of nephrosclerosis. The aim of this study was to evaluate the clinical significance of serum and urine levels of stable NO metabolites in patients with various clinical forms of chronic glomerulonephritis (CGN), as well as CGN patients with chronic renal failure (CRF). Ninety-seven CGN patients, including 56 ones with preserved nitrogen excretion and 41 ones with CRF, were examined. The levels of stable NO metabolites (nitrites and nitrates) in serum and 24-hour urine were measured. The highest serum and urine NO levels were found in patients with nephrotic and hematuric CGN; patients suffering from latent and hypertonic CGN displayed the lowest levels. Patients with CRF had higher serum levels of NO compared with non-CRF patients. A reverse correlation between serum levels of creatinine and NO in patients with CRF was revealed. In CGN patients without CRF, the activity of inflammatory process, observed by high C-reactive protein levels, was associated with elevation of blood and urine levels of NO, while such an association was not found in patients with CRF.

[Protective and damaging effects of periodic cerebral hypoxia: the role of nitric oxide].

Low oxygen delivery to organs and tissues is one of the most life-threatening situations. Periodic hypoxic episodes may have not only damaging, but also protective effects on the organism depending on how long and intensive this factor is. In both cases an important role is played by changes in the synthesis and metabolism of NO. The direction of NO synthesis and, finally, the direction of periodic hypoxia effect is determined by the regimen of hypoxic impact. The effect of NO depends on its concentration. Both NO excess and deficit are very unfavorable to the organism. Sleep apnea syndrome and pulmonary hypertension are typical examples of NO-dependent damaging effects of periodical hypoxia. NO-dependent protective effects of adaptation to periodic hypoxia are underlied by moderate stimulation of NO synthesis, which provides both compensation for NO deficit and the limitation of its hyperproduction. In turn, NO may increase the expression of other protective factors, which makes adaptive protection more reliable and durable. Understanding the mechanisms of adaptation to hypoxia will help develop new approaches to the prevention of hypoxia and ischemic lesions and the improvement of adaptive abilities of the organism.

[The effects of adaptation to hypoxia on the resistance to neurodegenerative disorders in the brain of rats of different genetic strains].

The aim of the study was to compare the protective effects of adaptation to altitude hypoxia (AH) on neurodegenerative brain disorders (NBD) induced with infusion of beta-amyloid peptides (Abeta) into the brain (imitation of Alzheimer's disease) of rats belonging to two species: Wistar rats (WR) and August rats (AR). Previously it was shown by the authors that WR were less resistant to memory function impairment and open-field activities, induced with Abeta infusion compared with AR. This study showed that preliminary AH significantly restricted brain function impairment induced by Abeta in WR, so AH demonstrated the protective effect in WR. In contrast, in AR preliminary AH provoked those impairments induced by Abeta. The AH protective effect in WR was associated with activation of stress-limiting systems (antioxidant system, NO system). Lack of AH protective effect in AR was associated with lack of activation of these systems in these rats. Thus, the different AH effects on NBD development in WR and AR are obviously determined by hereditary peculiarities of stress-limiting systems in WR and AR.

Role of heat shock proteins HSP70 and HSP32 in the protective effect of adaptation of cultured HT22 hippocampal cells to oxidative stress.

Preadaptation of cultured HT22 mouse hippocampal neurons to oxidative stress prevented cell damage induced by severe oxidative stress. This protection manifested in a decrease in metabolic disturbances in neurons. Adaptation of neurons to oxidative stress was accompanied by accumulation of HSP32 and HSP70. HSP synthesis inhibitor quercetin abolished the protective effect of adaptation under conditions of oxidative stress. Activation of HSP70 synthesis in neurons is an important mechanism for adaptive protection of cells.

Inversion of stress response reprogramming phenomenon in lipopolysaccharide-stimulated alveolar macrophages.

The stress response and NO production in reprogrammed proinflammatory or antiinflammatory alveolar macrophages were studied after lipopolysaccharide treatment. Experiments with macrophages not containing HSP70 showed that lipopolysaccharide in a dose of 500 ng/ml induced stress response in cells with the proinflammatory phenotype (as distinct from an antiinflammatory phenotype). The stress response was not observed in HSP70-containing lipopolysaccharide-stimulated proinflammatory macrophages, but occurred in cells with antiinflammatory phenotype. Hence, the presence of HSP70 in alveolar macrophages results in the inversion of the phenomenon of reprogramming of the stress response. Independently on the phenotype, stimulation with lipopolysaccharide was accompanied by a 60-70% increase in NO production by macrophages not containing HSP70. However, NO production by HSP70-containing macrophages did not increase in response to lipopolysaccharide treatment. Our results indicate that reprogramming of the cell response in macrophages does not concern the system for NO synthesis. HSP70 prevents the lipopolysaccharide-induced activation of NO synthesis in alveolar macrophages.

Intracellular and extracellular NO differentially modulates the stress response and apoptosis in macrophages exposed to the influence of biological or physical factors.

We studied the role of extracellular and intracellular NO in the regulation of the stress response and apoptosis in macrophages of proinflammatory and antiinflammatory phenotypes under the influence of S. aureus and heat shock. Blockade of extracellular nitric oxide synthesis in cells with antiinflammatory phenotype inhibited the stress response induced by S. aureus and heat shock. The decrease in extracellular nitric oxide concentration around antiinflammatory macrophages potentiated the stress response induced by S. aureus, but had no effect on the stress response induced by heat shock. Hence, intracellular NO mediates the stress response induced by S. aureus and heat shock, while extracellular NO inhibits the stress response induced by S. aureus, but has no effect on the stress response induced by heat shock. In cells with antiinflammatory phenotype, intracellular NO plays an antiapoptotic role. S. aureus and heat shock did not cause apoptosis in macrophages with proinflammatory phenotype, while intracellular NO did not play a role in antiapoptotic activity of the proinflammatory phenotype. Extracellular NO synthesized by macrophages protects these cells from apoptosis induced by S. aureus and heat shock.

Role of extracellular and intracellular nitric oxide in the regulation of macrophage responses.

We studied the role of nitric oxide in the stress response and apoptosis. Intracellular nitric oxide potentiated the stress response. However, intracellular nitric oxide suppressed the stress response in macrophages of proinflammatory and antiinflammatory phenotypes. Intracellular nitric oxide promoted apoptosis in macrophages of the proinflammatory phenotype, but inhibited this process in cells of the antiinflammatory phenotype. Exogenous nitric oxide synthesized by macrophages protected them from lipopolysaccharide-induced apoptosis. Our results indicate that nitric oxide produces various effects on the stress response and apoptosis in macrophages, which depends on modus operandi.

Mechanism of adaptation of the vascular system to chronic changes in nitric oxide level in the organism.

We studied the possibility of directed modulation of the efficiency of NO storage in rats due to adaptation to the chronic changes in plasma NO level. The efficiency of NO storage increased during long-term maintenance of high plasma level of NO and decreased in NO-deficient states. The compensatory changes in NO storage capacity of vessels depending on its organism content represent a new mechanism of adaptation of the cardiovascular system to chronic excess or deficit of NO, while directed modulation of this process can be important for the protection of the organism against both surplus or shortage of NO.

Adaptation to hypoxia prevents disturbances in cerebral blood flow during neurodegenerative process.

The rats with neurodegenerative brain disorder induced by administration of a toxic fragment of beta-amyloid demonstrate weakened endothelium-dependent dilation of cerebral vessels, which attested to impaired production of endothelial NO. At the same time, toxic beta-amyloid fragment induced the formation of NO depots in the walls of cerebral vessels, which indirectly attests to NO overproduction in the brain tissue. Preadaptation to hypoxia prevented endothelial dysfunction and improved the efficiency of NO storage. Our results suggest that adaptation to hypoxia protects the brain from various changes in NO production during neurodegenerative damage.